Waterproofing Technology for Cement Tile Sloped Roofs
This paper introduces the waterproofing technology for cement tile sloped roofs.
In accordance with codes and design requirements, and considering project characteristics, the roof adopts two waterproof layers:the first layer is a waterproof membrane system;the second layer is the finished cement tile roof.Throughout construction, tile quality and installation method must be strictly controlled to ensure the overall waterproof performance of the roof. 1 Roof Waterproofing Construction
The roof waterproofing structure is shown in Figure 1.The construction sequence is:leveling → cleaning → waterproof membrane → insulation layer → steel mesh concrete protective layer → 30‑mm‑thick 1:3 cement mortar leveling layer. The outer edge of the sloped roof in this project is raised by 80 mm to support the insulation board.A welded wire mesh of Φ6 @ 500×500 mm is laid over the insulation layer to restrain shrinkage cracking of the cement mortar. The leveling layer uses 30 mm thick 1:3 cement mortar. After application, the surface is roughed with a wooden float to ensure firm tile bonding and tight fitting to the roof.
Before construction, the base must be thoroughly cleaned, with no standing water left on the roof.Acceptance of the previous process shall be organized.Residual release agent, mortar and dust on the concrete base shall be removed;protrusions and honeycombing on the roof shall be repaired.The leveling layer shall be smooth, solid and firmly bonded to the base. The installation of cement tiles is the final step of roof construction.Before installation, the tile surface shall be cleaned, and the roof level, main ridge, hip ridges, and eave corners shall be checked for accuracy. The installation sequence is:base inspection and vertical layout → centering, ridge marking and tile spacing → main ridge setting → hip and ridge setting → side ridge laying → bottom tile laying → cap tile laying → joint pointing → cleaning. Key Installation Points
2.1 Base Inspection and Vertical Layout
Mark the vertical tile spacing with ink lines according to construction drawings, adjusting within effective dimensions as much as possible.A reverse edge is formed at the eave to ensure vertical and outward dripping. 2.2 Centering, Ridge Marking and Tile Spacing
Find the center point of the roof at the ridge (the midpoint of the center bottom tile)and the center point at the eave.Snap a line between these two points as the center line of the middle ridge.According to tile dimensions, arrange tiles from the middle ridge to both ends,keeping the number of bottom tile ridges odd. 2.3 Main Ridge Setting
Lay the bottom tiles of each ridge at the marked positions with full mortar; no looseness is allowed after laying.Then construct the main ridge ornaments and mark the hip ridge lines.The main ridge is a critical component with strict dimensional accuracy.Lay the first center ridge tile on the marked center line, then install tiles toward both ends. 2.4 Hip Ridge and End Ridge Setting
Hip ridges are divided into pre‑ornament and post‑ornament sections, with the front section accounting for 1/3 of the slope length.The hip ornament is placed at the boundary, and the angled overhang is installed at a specified projection length.End ridges are located at the four corners of hip roofs, with construction similar to hip ridges.Joints between end ridges and hip ridges must be tight to prevent cracks. 2.5 Side Ridge Laying
At both side ridges of the slope, lay angled drip tiles, bottom tiles and cap tiles.The curvature of both side ridges must be consistent and parallel.The curve of the side ridges sets the standard for the entire roof surface and directly affects overall quality. 2.6 Bottom Tile Laying
Tiles shall be delivered in an orderly and planned manner, symmetrically on front and rear slopes, not concentrated on a single slope, and reasonably distributed for operation.Lay bottom tiles according to the marked spacing, filling and securing with full mortar. The lap length of bottom tiles shall be properly controlled.Eave tiles shall project 5–6 cm beyond the eave.Before installation, the eave line shall be raised by 2 cm to keep the eave slightly outward.Tiles are laid with a 40% overlap ratio.Eave tiles shall be smooth, with consistent height and straight lines. Tiles shall be laid straight to ensure proper drainage, with uniform spacing.Damaged or cracked bottom tiles are strictly prohibited to prevent leakage. 2.7 Cap Tile Laying
Cap tiles are installed from bottom to top with joints upward; upper tiles overlap lower ones.Joints are filled with sufficient mortar and compacted.Joint width shall be uniform and no more than 5 mm — a key measure to prevent leakage. Mortar for ridge tiles shall be full, and joints straight.A 1.5‑m wooden strip is used to align and straighten tiles during construction.The tile surface shall be level laterally and smoothly curved longitudinally. When the roof slope exceeds 30°:
Pre‑embedded double 18# copper wires are tied to tile battens and tiles.
Tiles are bedded in cement composite mortar (cement : sand : clay paste = 1 : 6.83 : 0.659).
The bedding layer shall be full, with a minimum thickness of 20 mm.
All tiles must be firmly fixed without detachment or looseness.
2.8 Joint Pointing
Clean the ridges thoroughly.Use colorants matching the cement tiles, mixed into white cement mortar to a similar shade.Wipe the tile surface clean in time to avoid staining. Conclusion
By implementing the above method and strictly following the construction process,with full mortar under tiles and flat, tight joints,the project was inspected and accepted by the quality inspection station, the client and the supervision unit.All parties confirmed that:the cement tiles are tightly overlapped,waterproofing performance is excellent,lines are smooth,ridges and valleys are straight,and the overall appearance is attractive.
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